Scientia Iranica
Volume:20 Issue: 3, 2013

This review briefly describes the concerns of nanobiotechnology in the design and development of novel vaccines using the most known nanocarriers, including nature-made nanocarriers (such as bacterial spores, virus-like particles, exosomes, and bacteriophages), man-made nanocarriers (such as Proteosomes, liposomes, virosomes, SuperFluids, and nanobeads), and their applications in therapeutic and protective immunization, as well as their advantages and disadvantages. Here, we focus on the development of nano-based vaccines as “nanovaccines” for inducing immune systems, and the foreseeable promises and problems when compared with existing vaccines. Also, we review a potential nano-hazard for vaccines, so-called nanobacterial contamination.

We have performed Density Functional Theory (DFT) calculations to investigate the influence of carbone nanotube (CNT) size on the properties of the electronic structure of various junction models constructed from (6, 0) CNT and graphene nanoribbon (GNR) units via covalent linkage. Chemical shielding tensors and the HOMO–LUMO gap have been calculated for different models of the investigated hybrids of CNT and GNR. Our results indicate that the HOMO–LUMO gap strongly depends on the number of atoms and tube length, showing a decreasing trend with increasing the length of the tube and approaching zero in Model 7. The isotropic and anisotropic Chemical Shift (CS) parameters are divided into some layers, based on detecting similar electronic environments for the atomic sites of each layer.

5% (molar ratio) Fe doped TiO2 nanoparticles were prepared by a sol gel method and the post annealing of the samples was carried out at 400 °C, 600 °C and 800 °C in air. Structural characterization of the samples was carried out using High Resolution Transmission Electron Microscopy (HRTEM). HRTEM images of the samples revealed that the mean size of the nanoparticles changed from ∼8 nm to ∼100 nm as the annealing temperature was increased. Experimental investigation of the electronic structure of TiO2:Fe nanoparticles is important in order to understand the correlation between electronic and optical properties in these samples. X-ray Photoemission Spectroscopy (XPS) of the TiO2:Fe nanoparticles was performed to study the electronic structure. The results of XPS study confirmed the presence of Fe in all samples, which could not be detected by HRTEM and XRD, in spite of low doping levels, and revealed that Fe ions are predominantly in Fe3+ states. Photoluminescence (PL) measurements have been measured with an excitation energy of 250 nm to study optical properties of the TiO2:Fe nanoparticles. The active PL band at ∼440 nm has been observed.

The thermal stability of Poly (L-lactide) PLLA biocompatible and biodegradable polymer reinforced with functionalized Multiwalled carbon nanotubes (MWCNTs) was investigated. For improvement of MWCNTs, the pristine MWCNTs (pMWCNTs) were functionalized, at first, by Friedel Crafts acylation, which introduced the aromatic amine groups on the side wall of MWCNTs (MWCNT- NH2) without shortening or cutting of pMWCNTs. Then, the PLLA chains were covalently grafted from the sidewall of MWCNT- NH2 by in situ ring-opening polymerization of L-lactide oligomers (LA), using stannous octanoate as the initiating system (MWCNT-g-PLLA). The FT-IR and XPS spectra revealed that the PLLA chains grafted strongly from the sidewall of MWCNTs. The thermo-gravimetric analysis of prepared composites with various concentrations of MWCNT-g-PLLAs shows a significant increment in the thermal stability of composites, by increasing the concentration of MWCNT-g-PLLAs in composites. The XRD analysis revealed that the MWCNT-g-PLLAs increased the crystallinity of PLLA, indicating that the composites with PLLA grafted MWCNTs were more thermally stable than those of neat PLLA.

Alginate-SBA-15 (ALG-SBA-15) was synthesized by encapsulation of the nanoporous SBA-15 in the biopolymeric matrix of calcium alginate. This adsorbent was characterized using powder X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), nitrogen adsorption-desorption and Fourier transform infrared (FT-IR) spectroscopy. Tests were then conducted to study the adsorption of lead ions onto ALG-SBA-15 from an aqueous solution for the effect of pH, contact time and temperature in batch systems. Freundlich and Langmuir models were used for a mathematics description of the adsorption isotherm. The equilibrium process was described well by the Langmuir isotherm model with the maximum sorption capacity of 222.22 mg g−1 of lead on ALG-SBA-15. The kinetics analysis revealed that the overall adsorption process was successfully fitted with the pseudo-second-order kinetic model. The values of calculated thermodynamic parameters (image, image and image) indicated the endothermic and spontaneous nature of adsorption. All the results validated the feasibility of ALG-SBA-15 for highly effective removal of lead from an aqueous solution.

Brucellosis is a zoonosis disease of worldwide importance among animal and humans. The most important virulence factor of Brucella spp. is related to its intramachrophage survival. On the other hand, because of the side effects of the current brucellosis treatment regime, it is necessary to find out new antimicrobial agents to treat the disease. The aim of this study is to investigate the antibacterial effect of silver nanoparticles against Brucella under an intramacrophage condition. A well diffusion agar test showed the activity of silver nanoparticles against Brucella melitensis 16M. Macrodilution experiments demonstrated the MIC and MBC of silver nanoparticles 4 and 6 ppm, respectively. The incubation time study showed that silver nanoparticles were able to kill bacteria within 40 min after the reaction. The cell culture study revealed that silver nanoparticles have effective antimicrobial activity inside the macrophage cells in concentrations of 4–6 ppm and the findings showed that one may consider silver nanoparticles as a new nano drug against intramachrophage Brucella melitensis 16M.

Synthesis of ZnO nanostructures was achieved on glass substrate by the resistive evaporation of metallic zinc granules followed by dry oxidation process at 350, 450 and 550 °C. Characterization of the products with FESEM and TEM revealed that the structures obtained at 450 °C are mostly nanorods with diameters between 40 and 105 nm and lengths from 1 to 5 μm. One dimensional ZnO nanostructures such as ultra thin nanobelts, nanowires and nanorods were successfully synthesized at 550 °C, with lengths up to several micrometers. XRD patterns indicated that the structures are crystalline and that ZnO nanostructures grown at 550 °C are fully oxidized and are crystalline with wurtzite hexagonal structure. PL measurements were carried out at room temperature and they revealed that there are three band emissions; one sharp strong peak in the UV region and two weaker peaks in the visible region. A strong UV emission was observed in the spectra of the ZnO nanorods and nanowires which confirms the good optical properties of products. The PL spectra also exhibited a considerable shift toward the shorter wavelength in the UV region. It is clear that after the second annealing step photoluminescence of the 1D nanostructures, fabricated at 550 °C, have improved, especially in the UV region.

Use of various plant materials for the biosynthesis of nanoparticles is considered a green technology, as it does not involve any harmful chemicals. The present study reports that silver nanoparticles (Ag NPs) were synthesized from a silver nitrate solution by commercially available plant powders, such as Solanum tricobatum, Syzygium cumini, Centella asiatica and Citrus sinensis. Ag NPs were characterized by UV–vis spectrophotometer, X-Ray Diffractometer (XRD), Atomic Force Microscopy (AFM) and fourier transform infrared (FTIR) spectroscopy. The formation and stability of the reduced silver nanoparticles in the colloidal solution were monitored by UV–vis spectrophotometer analysis. The mean particle diameter of silver nanoparticles was calculated from the XRD pattern, according to the line width of the plane, and the refraction peak, using Scherrer’s equation. AFM showed the irregular shapes of Ag NPs, and the formation of silver nanoparticles was found to be 53, 41, 52 and 42 nm, corresponding to Syzygium cumini, Citrus sinensis, Solanum tricobatum and Centella asiatica, respectively. FTIR spectroscopy confirmed the presence of protein as the stabilizing agent surrounding the Ag NPs. Antimicrobial activity of the silver bio-nanoparticles was performed by a well diffusion method. The highest antimicrobial activity of Ag NPs synthesized by C. sinensis and C. asiatica was found against Pseudomonas aeruginosa (16 mm). The Ag NPs synthesized in this process were found to have efficient antimicrobial activity against pathogenic bacteria.

Copper oxide (CuO) nanoparticles and nanolayers were synthesized by sol–gel and spray pyrolysis methods, respectively. The structure and morphology of the prepared samples were characterized using XRD, SEM and TEM analysis. Aspergillus niger fungi were grown in an appropriate medium and exposed to the synthesized samples in a closed glass vessel. The boisoning properties of the nano systems were investigated by measuring their electrical resistance at regular time intervals and different temperatures. Further studies were made on the effects of CO2 and humidity on the sensing properties, using CaCo3 and Silica gel. The considerable changes observed in the electrical resistance of the prepared samples, in the presence of Aspergillus niger fungi, support our proposed system as a biosensor.

In this paper, a reliable algorithm based on new homotopy perturbation transform method (HPTM) is proposed to solve a nonlinear differential-difference equation arising in nanotechnology. Continuum hypothesis on nanoscales is invalid, and a differential-difference model is considered as an alternative approach to describing discontinued problems. The HPTM is a combined form of Laplace transform, homotopy perturbation method and He’s polynomials. The technique finds the solution without any discretization or restrictive assumptions and avoids the round-off errors. The numerical solutions show that the proposed method is very efficient and computationally attractive. It provides more realistic series solutions that converge very rapidly for nonlinear real physical problems.

Silicon nanocrystals with dimensions of about 3 to 4 nm are fabricated by hydrogenation of amorphous silicon layers with thickness of about 15 nm. The strong binding of nanocrystals to the amorphous matrix, which prevents them from showing luminescence, is broken up by a plasma treatment process in the presence of H2, N2O, and SF6. Regions with high nanocrystal density show more resistance against plasma etching. By controlling the etching parameters such as precursor flow rates during hydrogenation and plasma treatment processes, it seems possible to realize luminescent layers. Photoluminescence (PL) studies show that nanocrystals emit light around a wavelength of 550 nm. Multilayer structures have been fabricated to increase the PL intensity by separating luminescent nanocrystal layers with a 5 nm-thick layer of silicon oxynitride. The entire fabrication process has been performed in a conventional RF-PECVD reactor offering hope for realization of cost-effective silicon light-emitting structures. The low temperature nature of the proposed process could lead to the fabrication of light-emitting devices on low cost substrates like glass or even plastic.

The biomedical image-type titanium alloy Ti–29Nb–13Ta–4.6Zr (TNTZ) exhibits non-toxicity and a low Young’s modulus that is similar to that of bone. This alloy has a low Young’s modulus because it contains a metastable image phase. Strengthening due to grain refinement tends to provide high mechanical strength, while keeping the Young’s modulus low, because it maintains the original image phase. In this case, severe plastic deformation, such as High-Pressure Torsion (HPT), is a potential treatment for obtaining these properties simultaneously. Thus, in this study, the effect of HPT on the microstructure and hardness of TNTZ was systematically investigated. On the cross sections of TNTZ subjected to HPT, heterogeneous microstructures, consisting of a matrix and an unetched band not corroded by an etching solution, were observed. Both the matrix and the unetched band were comprised of a single image phase with submicron-sized grains, but their grain geometries differed: equiaxed grains and elongated grains are observed in the matrix and the unetched band, respectively. The hardness distribution in the cross section of TNTZ subjected to HPT is also heterogeneous; the hardness is higher in the matrix than in the unetched band, when the number of HPT rotations is small.

Nano layers of zinc, which were deposited by magnetron sputtering on Si (100) substrate, thermal oxidation exposed to the air at 400 °C, were employed to produce ZnO thin films. In order to study the influence of the deposition rate on surface morphology, samples with different deposition rates (1.2–4.5 nm/s) were produced. The surface characteristics of these ZnO thin films are then evaluated against data which result from Atomic Force Microscopy (AFM). The results demonstrate that the film deposited with higher rates has higher surface roughness and grain size. The fractal analysis illustrates that the roughness exponents (image) for all samples are close.